While both quantum physics—in the form of the Standard Model of particles and interactions—and gravitation—formulated in general relativity—are hugely successful theories, making them work together hasn't, well, worked out. Currently, there's no complete, reliable quantum theory of gravity, though there are many candidates, including superstring theory. In most of these schemes, quantum behavior extends to spacetime itself, setting a fundamental length at which gravitation modifies quantum theory. This fundamental scale, known as the Planck length, is beyond the reach of foreseeable experiments.

However, a related quantity known as the Planck mass may provide another way to check for quantum gravity in the laboratory. As proposed by Igor Pikovski, Michael R. Vanner, Markus Aspelmeyer, M. S. Kim, and Časlav Brukner, it should be possible to reach the Planck mass experimentally: instead of creating individual particles with the vast amounts of energy necessary to access it, experiments can instead involve ensembles of particles with a total mass that is on the order of the Planck mass. In this way, modern experimental techniques in quantum optics can be used to test potential modifications of the famous Heisenberg uncertainty principle that arise due to quantum gravity.

The Standard Model of particles and interactions stands as a powerful and successful quantum theory that describes the fundamental building blocks of nature. However, it deals with the electromagnetic and nuclear forces only; gravity is not included. There are a number of proposals on how to unify the two.

In some versions of quantum gravity, spacetime is like the boxes on a sheet of graph paper, and everything is limited to happening at the corners. Each of the corners is separated by the same distance: the Planck length, which is 1.6 x 10-35 meters—far smaller than atomic nuclei.

In ordinary quantum theory, there isn't any fundamental length scale. In fact, the Heisenberg uncertainty principle, which states there is a limit to how precise length and momentum measurements can be, is incompatible with a fundamental limit like this. Thus, quantum gravity demands a modification of the uncertainty principle, though it doesn't tell us what form the modification should take. However, if the effect is large enough, sensitive experiments may be able to detect deviations from the ordinary uncertainty principle.

Energy and length have a reciprocal relationship: to probe tiny length scales requires a lot of energy. The best particle colliders (such as the Large Hadron Collider [LHC]) can reach very high energies and thus small lengths, but are still very far from reaching the Planck scale. However, as Pikovski et al. note, Einstein's famous formula E = mc2 shows that large energy E also relates to large mass m. Although we can't create single particles that are massive enough, even in the LHC, there are some quantum systems in which a collection of particles act as a single object.

The type of hypothetical experiment described by Pikovski et al. would use the extremely precise methods of quantum optics. Rather than trying to access the Planck length directly (which would require prohibitively large energies), they note that the Planck mass is a relatively large 22 micrograms (22 μg). While that is far heavier than any elementary particle, modern condensed matter physicists have prepared ensembles of particles with total masses in that range.

The researchers propose creating a quantum oscillator with enough mass by controlling large numbers of particles with light (a fairly common technique). We should then be able to test if its response is different from what is predicted in the ordinary Heisenberg uncertainty principle.

In most respects, the proposed experiments are the opposite of what we usually do when we test the Standard Model in things like particle accelerators. To prepare the ensemble of particles into the appropriate quantum state will require cooling the system down to less than a tenth of a degree above absolute zero. However, quantum optics labs are far more manageable than particle accelerators, so these experiments may be doable at many modern universities.

If the experiments can be performed to the required precision, then it might not only be possible to detect quantum-gravitational effects, but we could potentially rule out some proposed versions of quantum gravity. That alone is an exciting possibility: as conventionally understood, most quantum gravity models are so far out of experimental reach as to be nearly metaphysical.

"as conventionally understood, most quantum gravity models are so far out of experimental reach as to be nearly metaphysical untestable/unfalsifiable. "

All scientific theories have a metaphysical doctrines built into them.

Perhaps the presuppositions but the predictions should not to be *nearly* metaphysical. I have no objection to your reformulation but I'm not sure it adds anything to the metaphorical expression used by the author.

"as conventionally understood, most quantum gravity models are so far out of experimental reach as to be nearly metaphysical untestable/unfalsifiable. "

All scientific theories have a metaphysical doctrines built into them.

Perhaps the presuppositions but the predictions should not to be *nearly* metaphysical. I have no objection to your reformulation but I'm not sure it adds anything to the metaphorical expression used by the author.

One of them is true and makes sense. The first formulation doesn't. It's an easy choice.

Quantum gravity implies that the universe operates as a hyper-Planck-retina voxel display, with a Heisenberg blur on everything so that even if you could zoom in enough, you don't see any jaggies.

However, super-cold condensates might fuck with the level curve enough to reveal the pixelation of space-time.

Anyone want to go for a car analogy?

The majority of cars, trucks and bikes in America run on gasoline and it's something so monopolized and controlled by the oil companies in conjunction with the government that no matter where you look for, the only affordable engines you'll get are gas-powered.

However, advances in clean diesel techonology (and biodiesel for that matter) might fuck with that gasoline monopoly and reveal to the public that they've been ripped off all along.

"as conventionally understood, most quantum gravity models are so far out of experimental reach as to be nearly metaphysical untestable/unfalsifiable. "

All scientific theories have a metaphysical doctrines built into them.

Perhaps the presuppositions but the predictions should not to be *nearly* metaphysical. I have no objection to your reformulation but I'm not sure it adds anything to the metaphorical expression used by the author.

One of them is true and makes sense. The first formulation doesn't. It's an easy choice.

Not really. I mean maybe it's true for you but the rest of us with a little more sophistication seemed to understand just fine. And in fact if I were to be as pedantic as you your formulation is false. Scientific theories are built *upon* metaphysics, metaphysics is not built in. That's to say there are many different possible metaphysical foundation for a theory and the sinking of any particular metaphysical assumption isn't enough to sink a theory. Under your formulation they stand or fall together.

P.S. On reflection my original post was a little muddled. I meant that the predictions should not be tied to any particular metaphysics and the difference between saying nearly untestable and nearly metaphysical amounts to the same thing.

I am not arguing with an imbecile who cannot manage to be civil. Take that as a sign of your moral and technical superiority. You obviously need it. I will say in passing, if the level of spitefulness and righteous indignation you've demonstrated here is an indication of your real personality, you'd do well to log off and get yourself a life. Even if time weren't finite, I'd still have better things to do than to quibble with a childlike you.

I am not arguing with an imbecile who cannot manage to be civil. Take that as a sign of your moral and technical superiority. You obviously need it. I will say in passing, if the level of spitefulness and righteous indignation you've demonstrated here is an indication of your real personality, you'd do well to log off and get yourself a life. Even if time weren't finite, I'd still have better things to do than to quibble with a childlike you.

LOL. Yes, I may have been an ass but I provided some content to go with it. You yourself are doing precisely what you falsely accuse me of doing. Have you heard of a psychological theory called projection?

Yes, I may have been an ass but I provided some content to go with it. You yourself are doing precisely what you falsely accuse me of doing.

I don't even care about your awesome use of logic anymore. What I said is that if being right is the excuse you need to be an ass, you might want to reevaluate your priorities. On balance, showing your ass makes you look far more foolish.

Yes, I may have been an ass but I provided some content to go with it. You yourself are doing precisely what you falsely accuse me of doing.

I don't even care about your awesome use of logic anymore. What I said is that if being right is the excuse you need to be an ass, you might want to reevaluate your priorities. On balance, showing your ass makes you look far more foolish.

Fair. Being right isn't the most important thing in the world but neither is being courteous. Let's just say that your initial "correction" came across as condescending and pedantic without basis. If you are going to be a pedant you at least should be correct.

Translation:Quantum gravity implies that the universe operates as a hyper-Planck-retina voxel display, with a Heisenberg blur on everything so that even if you could zoom in enough, you don't see any jaggies.

Fair. Being right isn't the most important thing in the world but neither is being courteous. Let's just say that your initial "correction" came across as condescending and pedantic without basis. If you are going to be a pedant you at least should be correct.

There may come a day when we can meet here on friendlier terms but, for the time being, I will not be drawn into this shit again. We're done here. No more. Fini. I'm taking my ball and going home.

From my limited reading on this, it seems that Quantum Gravity may lead to the idea of Quantum Time and Quantum Space. That is, there is a smallest unit of space and there is a shortest unit of time. To me, as a layman, this should lead to the next great revolution in mathematics. I say this because as I understand it, The Calculus is based on the idea of reducing length or time to infinitely small units. But if this is correct - there is a hard limit of space and time beyond which you cannot go.

So, just as Newton was able to develop new physics and math in concert, I fully expect that Quantum Gravity will lead to a new fundamental math.

From my limited reading on this, it seems that Quantum Gravity may lead to the idea of Quantum Time and Quantum Space. That is, there is a smallest unit of space and there is a shortest unit of time. To me, as a layman, this should lead to the next great revolution in mathematics. I say this because as I understand it, The Calculus is based on the idea of reducing length or time to infinitely small units. But if this is correct - there is a hard limit of space and time beyond which you cannot go.

So, just as Newton was able to develop new physics and math in concert, I fully expect that Quantum Gravity will lead to a new fundamental math.

Or it could turn out to be a bad idea and nothing changes.

It has. One of the most redeeming qualities of superstring theory is the math that it has produced. In short the concept of instantaneous velocity doesn't make much sens within the context of quantum mechanics, nor do point particles, and thus superstring theory. I am not suggesting superstring theory is correct. I'm just saying that it's an acknowledgement that limits at infinity don't make much sense when talking about finite entities.

Sorry, you get that with the big collaborations. There's probably a new Heisenberg conjugate co-ordinate pair right there :

(number of authors) times (how much it makes sense) > constant :-)

Short summary : with the active damping of such a large interferometer ( 4km per side and heavy test masses ) you can get down to the low orders of quantum activation above ground state. A couple of hundred levels in this case. I don't think it was close enough to include/exclude new physics, but I believe that the current facility upgrades might when fully commissioned.

So this particle will be much more massive than the ones made by the LHC? Does that mean it's more likely to create a planet-ending black hole?

We're quite full of apocalypses right now thank you, we have an AGW thread running .... :-)

Seriously, it is mass/energy density that matters. If you get enough stuff within a given radius you can make your own at home. I'm about 90kg so if you can get all of me, oooh ... well within an alleged quark's width I'll either wink out of view and/or explode in a blaze of gamma rays. Either way I suggest that you run for it.

According to QES, relativity is formed from quantum causality. Only evolutionary causal interactions are observable as relativity. Systems of non-relativistic quantum causality form the interactive fabric of spacetime. String Theory and Higgs Field are perspectives of the quantum causality connections which are connected loops of moderated connections. Moderated by singularities (causal constants) forming physical constants.